Studies on nucleophilic substitution reactions with η6-o-dichlorobenzene-η5-cyclopentadienyliron hexafluorophosphate

Reaction of η6-o-dichlorobenzene-η5-cyclopentadienyliron hexafluorophosphate (IPF6) with an excess of phenol or p-thiocresol in the presence of K2CO3 could give disubstitution of both chloro groups of I, while a similar reaction with one equivalent of the nucleophile, and under conditions of high dilution, monosubstitution of only one of the chloro groups of I could be obtained. Similarly, di- or monosubstitution could be brought about under appropriate conditions with benzyl or methyl alcohol as the source of the nucleophile. While no reaction could take place between IPF6 and aniline, a reaction did occur between IPF6 and o-anisidine (o-methoxyaniline), but only the monosubstitution product was obtained, even in the presence of an excess of o-anisidine. Similar results of monosubstitution were observed with other nucleophiles containing the NH2 group, including NH3, NH2NH2, CH3NH2 and C6H5CH2NH2. These findings are consistent with the reported differences in yields when IPF6 was treated with two nucleophilic groups (OH, SH and/or NH2) located in the 1,2-positions of a benzene ring to give CpFe complexes of heterocyclic systems related to 9,10-dihydroanthracene with two hetero-atoms at the 9,10-positions [15]. Reactions were also carried out between IPF6 and the carbanion-enolate anion derived from acetylacetone, α-benzoylacetophenone, diethyl malonate or ethyl acetoacetate. In these cases, only monosubstitution of one of the chloro groups of I was observed, leading to the formation of a CC bond. A possible explanation for the formation of only monosubstitution products in reactions with N- or C-containing nucleophiles is discussed.